(1) Field of the Invention
The present invention relates to image forming devices that charge a surface of a photoreceptor, expose the surface of the photoreceptor to light to form an electrostatic latent image on the photoreceptor, develop the electrostatic latent image to form a toner image, transfer the toner image from the photoreceptor to a transfer target, and subsequently clean the surface of the photoreceptor by using a cleaning member.
(2) Description of the Related Art
In the field of image forming devices, as a method of charging a photoreceptor, a charging method is widely employed of physically contacting the photoreceptor with a charging member such as a charging roller.
This contact charging method can reduce environmental impact by producing a smaller amount of electrical discharge product such as ozone and NOx than a corona discharge method that uses a charger wire that does not physically contact the photoreceptor. However, even though the amount of discharge product is small, the discharge product easily attaches to the surface of the photoreceptor because the contact charging method uses physical contact between the photoreceptor and the charging member.
Discharge product attached to the surface of the photoreceptor can, for example, greatly lower electrical resistance when moisture is absorbed under high temperature and high humidity conditions, making the occurrence of disturbance (“image flow”) of an electrostatic latent image on the surface of the photoreceptor more likely.
As a method of cleaning discharge product from a photoreceptor, conventionally, a cleaning method is widely employed in which an end portion of a cleaning blade composed of a rubber such as polyurethane presses against the surface of the photoreceptor in a state of elastic deformation while the photoreceptor rotates. According to the frictional force between the surface of the photoreceptor and the cleaning blade, both the surface of the photoreceptor and the cleaning blade are very gradually worn away over a long period of time.
However, by adopting this configuration, a photosensitive layer of the photoreceptor is gradually worn away, and therefore stability of charging potential of the photoreceptor cannot be maintained over a long period of time, and product life of the photoreceptor is shortened.
Document JP 2011-95297 discloses a configuration intended to lengthen product life of a photoreceptor, according to which an organic photoreceptor is provided with a resin layer (hereafter, “overcoat layer”) on a photoreceptor layer to protect the photoreceptor layer, improving depletion and abrasion resistance of the photoreceptor layer.
However, a photoreceptor that has an overcoat layer as an outermost layer has a relatively high hardness, which causes only the cleaning blade composed of a rubber to be worn away by the frictional force.
According to a configuration of a photoreceptor that has an overcoat layer and a cleaning blade composed of a rubber, the cleaning method of cleaning off discharge product while the surface of the photoreceptor is gradually worn away is not possible, and therefore cleaning off discharge product only by using scraping force of elastic force of the cleaning blade becomes difficult, making accumulation of discharge product on the photoreceptor more likely.